good_price = float(input('请输入商品价格:'))
good_num = int(input('请输入商品数量:'))
total_price = good_num * good_price
discount_price = total_price*0.8 if total_price >= 100 else total_price
pay_money = float(input('请输入获取到金额:'))
out_money = pay_money - discount_price
if out_money < 0:
    print('还应该支付%f元哦' % abs(out_money))
else:
    print('应该找回' + str(out_money) + '元')
